4x+3y x= -3/4; y= -1/6
4*(-3/4)+3*(-1/6)=-3-1/2=-7/2
A*B2(A умножить на B в квадрате)
A3*B2
A2+B2
(A+B)2( A плюс B и всё в квадрате)
A2*B2
Ф3+B3
B* A3
![1)1+Ctg^{2}\alpha =\frac{1}{Sin^{2}\alpha} \\\\Sin^{2}\alpha=\frac{1}{1+Ctg^{2}\alpha}=\frac{1}{1+(-\frac{5}{12})^{2}}=\frac{1}{1+\frac{25}{144}}=\frac{1}{\frac{169}{144}}=\frac{144}{169}\\\\Sin\alpha =-\sqrt{\frac{144}{169} }=-\frac{12}{13}](https://tex.z-dn.net/?f=1%291%2BCtg%5E%7B2%7D%5Calpha+%3D%5Cfrac%7B1%7D%7BSin%5E%7B2%7D%5Calpha%7D+%5C%5C%5C%5CSin%5E%7B2%7D%5Calpha%3D%5Cfrac%7B1%7D%7B1%2BCtg%5E%7B2%7D%5Calpha%7D%3D%5Cfrac%7B1%7D%7B1%2B%28-%5Cfrac%7B5%7D%7B12%7D%29%5E%7B2%7D%7D%3D%5Cfrac%7B1%7D%7B1%2B%5Cfrac%7B25%7D%7B144%7D%7D%3D%5Cfrac%7B1%7D%7B%5Cfrac%7B169%7D%7B144%7D%7D%3D%5Cfrac%7B144%7D%7B169%7D%5C%5C%5C%5CSin%5Calpha+%3D-%5Csqrt%7B%5Cfrac%7B144%7D%7B169%7D+%7D%3D-%5Cfrac%7B12%7D%7B13%7D)
2) 25Cos²α - 5Cosα - 12 = 0
Обозначим Cosα = m , - 1 ≤ m ≤ 1
25m² - 5m - 12 = 0
D = (- 5)² - 4 * 25 * (- 12) = 25 + 1200 = 1225 = 35²
![m_{1}=\frac{5+35}{50}=\frac{4}{5}=0,8\\\\m_{2}=\frac{5-35}{50}=-0,6\\\\Cos\alpha=0,8\\\\\alpha=+-arcCos0,8+2\pi n,nez\\\\Cos\alpha =-0,6\\\\\alpha=+-arcCos(-0,6)+2\pi n,nez](https://tex.z-dn.net/?f=m_%7B1%7D%3D%5Cfrac%7B5%2B35%7D%7B50%7D%3D%5Cfrac%7B4%7D%7B5%7D%3D0%2C8%5C%5C%5C%5Cm_%7B2%7D%3D%5Cfrac%7B5-35%7D%7B50%7D%3D-0%2C6%5C%5C%5C%5CCos%5Calpha%3D0%2C8%5C%5C%5C%5C%5Calpha%3D%2B-arcCos0%2C8%2B2%5Cpi+n%2Cnez%5C%5C%5C%5CCos%5Calpha+%3D-0%2C6%5C%5C%5C%5C%5Calpha%3D%2B-arcCos%28-0%2C6%29%2B2%5Cpi+n%2Cnez)